Australia’s conservative coalition government was thrown into turmoil on Friday after the country’s high court ruled that five politicians, including the deputy prime minister and four other senators, had been disqualified from office. The decision could bring down Prime Minister Malcolm Turnbull’s ruling coalition, which so far has relied on a slim majority of only one seat.

The five politicians were found guilty of having violated the Australian constitution — written when the territory still consisted of several British colonies — which bans anyone from parliamentary office who is “citizen or entitled to the rights or privileges of a subject or a citizen of a foreign power.”

In a nation where many have parents who emigrated from overseas and where about a fourth of all citizens were born abroad, the ban’s strict enforcement has escalated into a debate about whether full loyalty to a country can only be ensured through single citizenship.

Similar laws that prohibit politicians or presidents from holding multiple citizenships exist in other countries, and “birther controversies” have at times also dominated the U.S. election cycle. Republican candidate Ted Cruz renounced his Canadian citizenship to quell claims that he could not become president because of his Canadian birthplace. Long before he became president, Donald Trump was also fueling rumors that then-President Barack Obama might not have been born in the U.S.

Australian Deputy Prime Minister Barnaby Joyce reacts as he sits behind  Prime Minister Malcolm Turnbull  at Parliament House in Canberra on Oct. 24, (Lukas Coch/AAP/Reuters)

In contrast, the birther controversy which might bring down the Australian government was partially brought up by the politicians under investigation themselves. Deputy Prime Minister Barnaby Joyce was born in Australia, but automatically held New Zealand citizenship because his father was born there. He renounced his second citizenship after claiming to have found out about it this August, but a court disqualified him from office, anyway.

The four other senators who were ruled ineligible to sit in federal parliament had similarly become citizens of Britain, Canada or New Zealand by descent or birth. All of them claimed not to have known about those second citizenships, and some of them had already resigned prior to Friday’s court ruling.

The crisis which has engulfed the Australian government is a cross-party problem, which emerged earlier this year when two senators of the Greens opposition party resigned from parliament after learning that they too held multiple citizenships. At the time, the Turnbull lashed out at these opposition politicians for having shown “incredible sloppiness.”

He likely later regretted his choice of words when he learned that his own deputy, Joyce, had the same problem. Ironically, Joyce himself had also previously slammed the two Greens party senators, saying that “ignorance is not an excuse.” Unlike them, however, Joyce refused to resign upon finding out about being guilty of the same “ignorance,” in order to prevent a collapse of the coalition government.

Throughout the summer, more senators across various parties revealed that they too were citizens of other countries. Joyce’s own deputy in his function as leader of the Nationals party later came out as British, although she has since renounced her citizenship. Some of those accused had more credible claims about having been unaware than those who were born or even raised abroad. Almost all of them tearfully expressed shock and remorse amid the revelations, even as they hoped to survive them.

As deputy prime minister, it was Joyce’s extra citizenship that hit the ruling coalition hardest. It also resulted in a diplomatic row with Australia’s close ally New Zealand, where a Labour party member of parliament brought up questions over Joyce's citizenship for the first time in public. The parliamentary scrutiny there came as a more discreet Australian investigation was already underway, but before Joyce had publicly acknowledged it.

Australian Foreign Minister Julie Bishop hit back at the time, saying that the questions brought up in New Zealand's parliament were “allegations designed to undermine the government of Australia,” and that she would find it hard to establish working relations should the New Zealand Labour party become part of the country’s next government. Turnbull later joined the diplomatic spat, claiming that the allegations amounted to a “conspiracy.”

The allegations ultimately proved to be correct, however, according to Australia’s high court — throwing the country into an uncertain political future. (The five politicians who have been disqualified from office could run again in future elections if they renounced their second citizenships and some, including Joyce, have already announced the intention to do so.)

Joyce will now have to compete in by-elections for his old seat. If he loses, the government would likely collapse.

And now, likely much to the chagrin of Australia’s governing coalition, New Zealand’s Labour party has become part of the government and their leader, Jacinda Ardern, the prime minister. Meanwhile, it is not entirely clear that Australia's Conservative Party will be staying in power itself.